u/Glittering-Middle200

Hi. I have this Hydroflask that my grandmother gave me not too long ago (maybe 2 years ago). I had filled it with water, drank some, and then forgot about it for probably over 5 months. It's just been sitting on my desk. Today, I finally decided to clean it and when I opened it, all you could see was just black mold everywhere. I'm worried I may not be able to clean all of it out and risk getting sick if I use it again. Do y'all think it is salvageable or should I just throw it out? I really don't want to throw it out since it was a gift, but if I cannot safely use it again I will have to.